scholarly journals Nanothermodynamic Description and Molecular Simulation of a Single-Phase Fluid in a Slit Pore

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 165
Author(s):  
Olav Galteland ◽  
Dick Bedeaux ◽  
Signe Kjelstrup
Keyword(s):  
Single Phase ◽  
Chemical Potential ◽  
Confined Fluids ◽  
Surface Areas ◽  
Confined Fluid ◽  
Consistent Manner ◽  
Slit Pore ◽  
Slit Pores ◽  
Differential Properties ◽  
First Time

We have described for the first time the thermodynamic state of a highly confined single-phase and single-component fluid in a slit pore using Hill’s thermodynamics of small systems. Hill’s theory has been named nanothermodynamics. We started by constructing an ensemble of slit pores for controlled temperature, volume, surface area, and chemical potential. We have presented the integral and differential properties according to Hill, and used them to define the disjoining pressure on the new basis. We identified all thermodynamic pressures by their mechanical counterparts in a consistent manner, and have given evidence that the identification holds true using molecular simulations. We computed the entropy and energy densities, and found in agreement with the literature, that the structures at the wall are of an energetic, not entropic nature. We have shown that the subdivision potential is unequal to zero for small wall surface areas. We have showed how Hill’s method can be used to find new Maxwell relations of a confined fluid, in addition to a scaling relation, which applies when the walls are far enough apart. By this expansion of nanothermodynamics, we have set the stage for further developments of the thermodynamics of confined fluids, a field that is central in nanotechnology.

scholarly journals Mechanical and Thermoelectric Properties of Bulk AlSb Synthesized by Controlled Melting, Pulverizing and Subsequent Vacuum Hot Pressing

2019 ◽  
Vol 9 (8) ◽  
pp. 1609 ◽  
Author(s):  
A. K. M. Ashiquzzaman Shawon ◽  
Soon-Chul Ur
Keyword(s):  
Mechanical Properties ◽  
Intermetallic Compound ◽  
Thermoelectric Properties ◽  
Hot Pressing ◽  
Single Phase ◽  
Aluminum Antimonide ◽  
Simple Method ◽  
Group Iii ◽  
Indirect Band Gap ◽  
First Time

Aluminum antimonide is a semiconductor of the Group III-V order. With a wide indirect band gap, AlSb is one of the least discovered of this family of semiconductors. Bulk synthesis of AlSb has been reported on numerous occasions, but obtaining a single phase has always proven to be extremely difficult. This work reports a simple method for the synthesis of single-phase AlSb. Subsequently, consolidation was done into a near single-phase highly dense semiconductor in a form usable for thermoelectric applications. Further, the thermoelectric properties of this system are accounted for the first time. In addition, the mechanical properties of the intermetallic compound are briefly discussed for a possibility of further use.

Ion size effect on chemical bonds of the RBa2Cu2.9Zn0.1Oy system

2018 ◽  
Vol 33 (3) ◽  
pp. 209-215
Author(s):  
R. Benredouane ◽  
C. Boudaren
Keyword(s):  
Single Phase ◽  
Rietveld Method ◽  
Solid State Reaction Method ◽  
X Ray ◽  
Bond Angles ◽  
Bond Valence Sum ◽  
Ion Size ◽  
First Time ◽  
Unique Variation ◽  
Strong Curvature

Single-phase polycrystalline samples of RBa2Cu2.9Zn0.1Oy (R = Y, Nd, Gd, Er, and Tm) (ZnR123) were synthesized using the standard solid-state reaction method. They were characterized by X-ray powder diffraction (XRD) and scanning electron microscope. XRD shows that all samples consist essentially of a single phase and retain the orthorhombic structure. The structure of the samples was refined by the Rietveld method with the help of the bond valence sum method. The variation of the lattice parameters and some meaningful bond angles and lengths with the ionic radius are discussed. In these compounds, the variations of the buckling angles Cu2–O(2,3)–Cu2 and Cu2–Cu2–O(2,3) are unique: the bond angles Cu2–O3–Cu2 and Cu2–Cu2–O2 increase, whereas the bond angles Cu2–O2–Cu2 and Cu2–Cu2–O3 decrease. The variation of these bond angles brings about a strong curvature of the Cu2O plane. Furthermore, we have found tree fixed triangles formed by the Cu2, O2, and O3 atoms in addition to another fixed triangle O1–Ba–O1 observed for the first time. BVS of Cu2 atom shows a specific and unique variation compared with other compounds.

scholarly journals A preliminary investigation of the molten salt mediated synthesis of Gd2TiO5 ‘stuffed’ pyrochlore

MRS Advances ◽  
2021 ◽  
Author(s):  
D. A. Austin ◽  
M. Cole ◽  
M. C. Stennett ◽  
C. L. Corkhill ◽  
N. C. Hyatt
Keyword(s):  
Molten Salt ◽  
Single Phase ◽  
Preliminary Investigation ◽  
Pyrochlore Phase ◽  
Comparative Investigation ◽  
Molten Salt Synthesis ◽  
Control Rods ◽  
First Time ◽  
Conventional Solid State Synthesis ◽  
Nuclear Applications

Abstract Refractory ‘stuffed’ pyrochlores such as Gd2TiO5 are of interest for nuclear applications, including as matrices for actinide disposition and as neutron absorbers in control rods. Here, we report the results of a preliminary comparative investigation of the synthesis of Gd2TiO5 by molten salt and conventional solid-state synthesis. We show that synthesis of Gd2TiO5 proceeds from the pyrochlore phase Gd2Ti2O7 which is first formed as a kinetic product. Molten salt synthesis afforded single phase Gd2TiO5 at 1300 °C in 2 h, via a template growth mechanism, and is effective for the synthesis of these refractory materials. This work demonstrates molten salt mediated synthesis of ‘stuffed’ pyrochlore for the first time. Graphic abstract

scholarly journals New metal-oxide composite materials as efficient catalysts of the partial oxidation of methane

2019 ◽  
Vol 484 (3) ◽  
pp. 299-302
Author(s):  
A. G. Dedov ◽  
O. A. Slyakhtin ◽  
A. S. Loktev ◽  
G. N. Mazo ◽  
S. A. Malyshev ◽  
...  
Keyword(s):  
Partial Oxidation ◽  
Single Phase ◽  
Complex Oxides ◽  
Partial Oxidation Of Methane ◽  
Metallic Nickel ◽  
Oxidation Of Methane ◽  
Nickel Cobalt ◽  
Phase Complex ◽  
First Time ◽  
Properties Of Composites

Single-phase complex oxides Nd2-yCayCoxNi1-xO4 have been synthesized for the first time. Composites prepared by the reduction of these compounds with hydrogen and containing Nd2O3, CaO, and cobalt and nickels metals have been used for the first time as catalysts of the partial oxidation of methane. The maximal methane conversions (97%) and syngas yields (96%) at 900 °С have been detected in the presence of the composite obtained from Nd1,5Ca0,5NiO4. At T < 850 °C, the nickel–cobalt composite synthesized from Nd1,3Ca0,7Co0,4Ni0,6O4 turned out to be more selective in the formation of syngas. Decreasing the partial oxidation temperature from 900 °С to 750 °С leads to the oxidation of metallic nickel and cobalt to oxides and to partial resynthesis of complex oxides with perovskite and K2NiF4 structures. The observed differences in temperature dependence of the catalytic properties of composites with various Ni/Co ratios can be associated with the participation of complex oxides in catalysis of the partial oxidation of methane at low temperatures.

9. pH Triggered Molecular Tweezers for Drug Delivery Applications

2016 ◽  
Author(s):  
Caitlin Miron
Keyword(s):  
Drug Delivery ◽  
Targeted Delivery ◽  
Chemical Potential ◽  
Cancer Drug ◽  
Molecular Tweezers ◽  
Binding Domains ◽  
Non Covalent Interactions ◽  
Molecular Tweezer ◽  
First Time ◽  
Covalent Interactions

Molecular tweezers are simple synthetic receptors that are generally composed of two binding domains connected by a spacer group. The non-covalent interactions that occur between the tweezer and its substrate are usually reversible, which facilitates the release of the bound substrate at a target site when triggered by a stimulus such as light, temperature, pH,] or change in chemical potential. In the field of cancer research, one strategy for targeting drug delivery relies on the pH drop in cancerous tissues compared to healthy tissues. We recently showed, for the first time, that it is possible to use pH to tune the binding affinity of molecular tweezers for substrates such as the cancer drug MitoxantroneTM. The molecular tweezer switches conformation from a closed (binding) state to an open (release) state upon acidification. As a result, the targeted delivery of MitoxantroneTM is achieved. This proof of concept shows that molecular tweezers are promising tools for selective drug delivery.

Critical Behaviour in Confined Systems

2005 ◽  
Author(s):  
Eldred H. Chimowitz
Keyword(s):  
Physical Adsorption ◽  
Chemical Separation ◽  
Main Question ◽  
Inorganic Membranes ◽  
Complex Materials ◽  
Fluid Mixture ◽  
Materials Engineering ◽  
Surface Areas ◽  
Confined Fluid ◽  
Two Phases

The prediction of properties in complex materials is a problem of importance in many applications in chemical and materials engineering; by the term “complex material” we mean a heterogeneous substance, like a porous material containing a confined fluid. Such materials appear in many technological applications, including: (1) processes using supercritical fluids to dry porous aeorogels and thin films [1], (2) physical adsorption of trace components from gaseous effluents, (3) gas storage using microporous materials [2], and (4) chemical separation using inorganic membranes [3]. Inorganic membranes are often highly porous and randomly structured materials with large surface areas available for adsorption, a property that makes them useful in chemical separation and as catalyst supports. In addition to their heterogeneity, complex materials have another distinguishing characteristic that relates to the structure of the heterogeneity itself. Is it periodic, or is it dispersed throughout in some random fashion? These two situations are quite distinct and may, in each instance, show critical behavior for a confined fluid belonging to entirely different universality classes, an issue that to the present time is still unsettled in the literature. In this chapter, we investigate the critical properties of fluids confined in randomly structured host materials like that found in porous silicon. The main question we address is: how does confinement in a porous structure affect the critical point or phase behavior of a fluid mixture? Before investigating some of the more advanced ideas in this area, we look at the basic thermodynamics of interfaces, and the phenomenon of capillarity in a single idealized pore structure. This simple example provides the impetus for a more detailed study of confinement effects. Consider two phases in equilibrium separated by an interface. The total energy of the composite system is the sum of the energy of each phase plus the energy associated with the interface. In formulating the fundamental thermodynamic equation for energy in this system, we presume that the formation of an interface requires energy; therefore, the energy equation must reflect this fact.

scholarly journals One-step ultra-rapid fabrication and thermoelectric properties of Cu2Se bulk thermoelectric material

RSC Advances ◽  
2019 ◽  
Vol 9 (19) ◽  
pp. 10508-10519 ◽  
Author(s):  
Tiezheng Hu ◽  
Yonggao Yan ◽  
Si Wang ◽  
Xianli Su ◽  
Wei Liu ◽  
...  
Keyword(s):  
High Temperature ◽  
Thermoelectric Properties ◽  
Single Phase ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Thermoelectric Energy ◽  
Rapid Fabrication ◽  
One Step ◽  
First Time

Cu2Se is a promising material for thermoelectric energy conversion. Fully dense single-phase bulk Cu2Se was prepared by the combination of self-propagating high-temperature synthesis with in situ quick pressing for the first time.

Confinement-induced modulation of elastic properties of nano-confined fluids in slit pore

2019 ◽  
Vol 28 (3) ◽  
pp. 036102 ◽  
Author(s):  
Zong-Li Sun ◽  
Yan-Shuang Kang ◽  
Yan-Mei Kang
Keyword(s):  
Elastic Properties ◽  
Confined Fluids ◽  
Slit Pore

scholarly journals Ga-Substituted Cobalt-Chromium Spinels as Ceramic Pigments Produced by Sol–Gel Synthesis

Crystals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1078
Author(s):  
Egle Grazenaite ◽  
Edita Garskaite ◽  
Zivile Stankeviciute ◽  
Eva Raudonyte-Svirbutaviciene ◽  
Aleksej Zarkov ◽  
...  
Keyword(s):  
Phase Composition ◽  
Crystallite Size ◽  
Single Phase ◽  
Sol Gel ◽  
Ceramic Pigments ◽  
Blue Color ◽  
Cobalt Chromium ◽  
Light Blue ◽  
Sol Gel Synthesis ◽  
First Time

For the first time to the best of our knowledge, cobalt-chromium spinels CoCr2−xGaxO4 with different amounts of gallium (x = 0–2 with a step of 0.5) were synthesized via the aqueous sol–gel route as ceramic pigments. The phase composition, crystallite size, morphological features, and color parameters of new compositions and their corresponding ceramic glazes were investigated using XRD, CIELab, SEM, and optical microscopy. It was demonstrated that the formation of single-phase CoCr2−xGaxO4 samples was problematic. Full substitution of Cr3+ by Ga3+ ion in the spinel resulted in the formation of light blue powders, which yielded violetish blue color for the corresponding ceramic glaze.

Mesoporous tantalum oxide photocatalysts for Schrauzer-type conversion of dinitrogen to ammonia

2005 ◽  
Vol 83 (4) ◽  
pp. 308-314 ◽  
Author(s):  
Chaoyang Yue ◽  
Michel L Trudeau ◽  
David Antonelli
Keyword(s):  
Surface Area ◽  
Tantalum Oxide ◽  
Catalytic Efficiency ◽  
Mesoporous Structure ◽  
Turnover Rates ◽  
Type Conversion ◽  
Electron Hole ◽  
Surface Areas ◽  
Before And After ◽  
First Time

Mesoporous tantalum oxide, Fe3+-doped mesoporous tantalum oxide, and bis(toluene) titanium reduced mesoporous tantalum oxide were used for the first time as Schrauzer-type photocatalysts for the conversion of dinitrogen to ammonia. The materials were characterized by XRD, TEM, XPS, and nitrogen absorption before and after catalytic runs. The results showed low to moderate activities depending on the composition. In contrast to previously studied Ti catalysts, Fe doping and heat pretreatment were not prerequisites for photocatalytic activity, but did improve the turnover rates by up to a factor of two. The optimal Fe loading for the tantalum oxides was found to be 1 wt% and the optimal heating condition at 300 °C for 3 h. Increased surface area and heat treatment were also found to improve activities. Contrary to our expectations, reduction of the mesostructure with bis(toluene) titanium had little effect on the catalytic activity. In spite of the dramatically higher surface areas of the mesoporous tantalum oxides as compared with bulk titanias used previously in this process, the overall catalytic activities were still less than those obtained in the Schrauzer system. This suggests that the increase in diffusion and surface area offered by the mesoporous structure is offset by the smaller crystalline domain sizes in the walls of the structure, leading to poor electron-hole separation and a reduction in catalytic efficiency. Key words: mesoporous, Schrauzer, ammonia, photocatalysis, tantalum oxide.

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